Solid propellant grains are required to be of uniform composition and to have good physical, chemical, and mechanical properties over a wide temperature range since the environmental conditions that solid propellant grains may be subjected to between the manufacturing date and the date used in a solid propellant rocket motor can vary considerably.
As the state-of-the-art has progressed in solid propellants various additives and processing aids to enhance properties or to improve processing conditions have been required. MT-4 is one such development which enhanced the mechanical properties when added to the propellant composition during the mixing thereof, in a trace amount from about 0.05 to about 0.5 weight percent of the propellant composition. The MT-4 serves as an interfacial bonding agent between the binder ingredients and the solid ingredients which include fine ammonium perchlorate, aluminum powder fuel, and optional additives. Although MT-4 improved the mechanical properties, it was found that a dispersing aid for the MT-4 was found to be necessary to ensure uniform coating of solids in the hydroxy-terminated polybutadiene binder system. Inadequate dispersion of MT-4 caused degradation of physical and mechanical properties and caused nullification of the function of MT-4 at low temperature.
Prior art dispersion adjuvants included trace amounts of "added" (to the MT-4) water, approximately 0.03% water based on propellant weight. Physical and mechanical property data confirmed that some of the curing agent was consumed by "added" water. The data also showed evidence when excessive amounts of "added" water is used that the bond at the AP interface is weakened and dewetting occurred at low temperature.
Desirable would be a dispersion aid for MT-4 which would react to become a part of the binder matrix without causing degradation of physical properties or nullification of the functions of MT-4 at low temperatures.
Therefore, an object of this invention is to provide a dispersion aid for MT-4 to ensure uniform coating of solids in a hydroxy-terminated polybutadiene bound solid propellant composition.
Another object of this invention is to provide a dispersing aid for MT-4 that enhances the propellant physical and mechanical properties by reacting to become a part of the binder matrix.